Apple's iPad Air 2. Source: Apple. 

Later this year, Apple (NASDAQ:AAPL) is expected to launch its next-generation iPad Air and iPad mini tablets. Given that Apple's iPad sales have continued to plunge over the last several quarters, with the year-over-year revenue decline steepening to 29% in the company's most recent quarter, Apple's going to bring extremely compelling products to the table with this year's iPad launches.

In this article, I'd like to make some educated guesses at which areas Apple will improve upon from last year's iPad Air 2 and iPad mini 3 with this year's devices.

iPad mini due for a complete makeover
The iPad mini 3 was a huge disappointment to many; Apple essentially took the iPad mini 2, included Touch ID, and offered the device in gold. It didn't, to my knowledge, bring any other improvements to the table.

This year, I suspect Apple will release a more compelling upgrade. A move to the A8 chip found inside of the iPhone 6/6 Plus would be nice, although the A8X would certainly be welcome. A move from 1 gigabyte of memory to 2 gigabytes, as we saw in the move from the iPad Air to the iPad Air 2, seems like a sensible move as well.

Additionally, a major criticism of the iPad mini 3 is the display. The display offers a very high resolution, but according to DisplayMate, it's severely lacking in many key areas. As a result of a narrow color gamut, DisplayMate says the colors on the device are "visibly washed out" and "distorted."

I'd be absolutely floored if Apple choses to ignore display quality on the next iPad mini.

I also expect Apple to transition from the old 802.11n Wi-Fi found in the iPad mini 2 and 3 to at least single-stream 802.11ac. Finally, I expect Apple to slim down the tablet's chassis from the relatively thick 7.5 millimeters (compared to the iPad Air 2, which is only 6.1 millimeters thick) it measures in at today.

iPad Air 3 doesn't need as much hardware work
The industrial design of the iPad Air 2 is superb, and I'm not convinced the company needs to make the device any thinner at this point. The improvements I hope to see aren't on the industrial design side of things.

One "obvious" improvement I'm expecting is an enhanced applications processor that will likely be called the A9X. The chip will surely have faster CPU cores, offer significantly enhanced graphics, and even more memory bandwidth -- the generational changes one would typically expect.

Apple might choose to go from two gigabytes of memory to, say, three or four in the next-generation iPad, but I don't think that upgrade will be necessary this time around.

Another area I think Apple will focus on is the display. In moving from the iPad Air to the iPad Air 2, Apple may have used the same display, according to AnandTech. The display is good, but AnandTech's review suggests there's a pretty big gap in quality/performance between the display found on the iPhone 6 and the iPad Air 2.

Given that the iPad Air 2 requires a much larger display than the iPhone 6/6 Plus do, it's probably cost-prohibitive to include a display of similar quality to modern iPhones on an iPad. That said, given that Apple needs to encourage customers to buy new iPads, I'm expecting a sizable jump in display performance in moving from the iPad Air 2 to the iPad Air 3.

The iPad Air 2 appears to support dual-stream 802.11ac, which is quite fast, so I'm not expecting Apple to upgrade the Wi-Fi in going to the iPad Air 3.

Apple may need to overhaul the iPad's UI
Although the iPad Air 2's hardware is solid, and the iPad Air 3's will surely be even better, Apple might consider significantly enhancing the user interface on the larger iPads.

Remember that one of the biggest criticisms of the iPad Air 2 from the WSJ's Joanna Stern was that the iPad Air 2 can only display one app at a time. This, she noted, is in contrast to competing tablets such as the Microsoft (NASDAQ:MSFT) Surface and the Samsung (OTC:SSNLF) Galaxy Tab.

If Apple introduces more aggressive multitasking/multi-window functionality, it would not only increase the demands on the processor/memory (potentially catalyzing iPad upgrades), but it would help further differentiate the iPad experience from, say, the iPhone experience.

Making the iPad an indispensable complement to the iPhone might help boost iPad sales even as iPhone sales continue to boom.